Alarm for a bicycle



FIG. 1 is a top plan view of an alarm for a bicycle showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side elevational view thereof, with the opposite side being a mirror image;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is a perspective view thereof. 

The ornamental design for an alarm for a bicycle, as shown and described. 